1. Field of the Invention
The present invention relates to a method for compensating carriage position of an ink jet printer, and more particularly to a method for sensing compulsory separation of a carriage from a home position in a stop state and compensating the home position by using a software method in an ink jet printer.
2. Discussion of Related Art
An ink jet printer has a carriage mounted on a main frame and moved right and left by a belt which is driven by a belt pulley, a head which is mounted on the carriage, moved together with the carriage and has a nozzle for discharging ink and a home position unit for cleaning the head in response to a cleaning signal at a predetermined cycle or capping the head.
In the printer of this type, if a print signal is applied, the carriage mounted on the main frame is moved right and left together with the head mounted thereon, and the nozzle of the head discharges ink onto the feeding paper, performing a printing.
The home position unit serves to clean the nozzle of the head to prevent the clogging thereof and to cap the nozzle while not printing after the printing operation to prevent the ink at the nozzle from being dried.
Whether or not the carriage is separated from home position is checked in the state when the carriage is positioned at the home position after printing operation. The position separation sensing method depends on the signal generated by a photo sensor and a code bar not on the driving signal provided by a microcomputer. FIG. 1 is a circuit diagram showing a conventional photo sensor unit, and FIG. 2 is a diagram showing a code bar generating an on/off signal.
Referring to FIG. 1, photo sensors A and B provide pulse waves which have a phase difference of 90 deg func{C} to an X axis channel and an Y axis channel. Capacitors C1 and C2 respectively connected to the photo sensors A and B serve to isolate signal noise generated at each photo sensor.
In this case, the phase difference of 90 deg func{C} is possible since the code bar 20 in FIG. 2 generates an on/off signal by the separated distance of the photo sensors A and B.
Referring to FIG. 2, the code bar 20 has a plurality of holes (21a, 21b, 21c . . .) and generates the on/off signal according to whether or not the light from the photo sensors A and B passes through the holes in the code bar 20.
If there occurs a signal change in the X and Y axis channels, the count value storing a carriage position value is increased or decreased by this change. Even though a user moves a motor by hand in a stop state when a driving signal is not generated after application of the power, the pulse signal is generated by the photo sensors A and B and the code bar 20, and thus the position count value of the motor is changed. Therefore, it is possible to sense whether or not the motor is compulsorily moved.
That is, with the circuit construction and code bar as described above, if the on/off pulse signal is not sensed at the X and Y axis channels, it is determined that the carriage of the printer is in a stop state. On the contrary, if the on/off pulse is sensed at the X and Y axis channels in the stop state, it is determined that the carriage is abnormally moved and thus a position compensating operation is performed.
The method for sensing carriage position separation as described above requires expensive components, such as two photo sensors and a code bar, etc, causing an increase of the manufacturing cost.